For centuries, physicians were trained in the basic humoral theory of disease according to Galen. The scientific method and introduction of quantitative evidence into physiological problems were William Harvey’s greatest contribution to medicine. Such investigations eventually led to the 1628 publication of one of the great books in Western medicine, Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus, or Anatomical Studies on the Motion of the Heart and Blood in Animals-often referred to simply as De Motu Cordis. The bleeding, cupping, emetics, or other treatments dictated by the long-held humoral theory were still used on patients. For doctors to completely discard the humoral theory with its attention to humors, innate heat, or pneuma, some viable alternative was needed to not just reject Galenic anatomy and physiology but to explain disease processes or, more specifically, the seat or starting place for disease. The anatomic concept of disease sent the humoral theory packing. Symptoms were of little use to the humoral theory of medicine. With the demise of the humoral theory, medicine moved towards a more modern age in the late 18th century.